The present invention relates to a film deposition method to form a copper (Cu) film on a substrate. In particular, the present invention is suitable for forming a Cu wiring film in a groove or a hole formed in a substrate, in which the groove or the hole having a relatively high aspect ratio.
VLSI have been integrated highly in recent years. This means that a wiring width of an integrated circuit becomes narrow. In connection with this, the requirements for the copper film deposition to provide wiring have changed.
Various methods are developed as the wiring technique with Cu, examples of which include: long throw sputtering, wet plating, ionized metal plasma (IMP) deposition, chemical vapor deposition (CVD). Each method is explained briefly for the case where a film is formed in the hole with a bottom.
The long throw sputtering is a deposition technique which takes a large target-substrate (T-S) distance for the sputtering. In other sputtering techniques, it is typically desirable to shorten the T-S distance as much as possible, thereby to broaden a distribution of a film thickness as well as to increase a deposition speed. However, this does not apply to the long throw sputtering for some reasons. The sputtering technique uses a carrier gas to release sputtered substances for deposition, so that the sputtered substances fly slant upward rather than perpendicular to the target. With a short T-S distance, the slant movement of the substances results in by far faster rate of deposition around the entrance to the hole than at the bottom and the entrance to the hole is clogged before the completion of the deposition on the bottom. In order to solve this problem, it is necessary to provide a good bottom coverage by using a technique performed with a large T-S distance to form a uniform film at a low speed. The reason why the long throw sputtering takes the large T-S distance lies in the above. Thus the long throw sputtering is disadvantageous in the low rate of deposition.
The wet plating is a technique to deposit a film by using an electrolysis in a liquid vessel. This method is more cost-effective in equipment as compared with a vacuum deposition apparatus and provides a high deposition process (400 nm/min or faster). However, the wet plating is inherently troublesome because it is performed in the atmosphere, comparative to other processes performed in vacuum. The wet plating also has problems of higher possibilities of contamination by foreign materials and voids in the resultant film. The film has only lower adhesion to SiO.sub.2 or a barrier metal (such as TiN and TaN). Furthermore, there exist the problem of complicated management of a layer as well as environmental problems in waste-fluid processing.
The IMP deposition is a technique in which a radio frequency is superposed on plasma in the deposition chamber for the sputtering to accelerate ionization of the flying substances. Ionized particles are withdrawn by using the electric field generated by a bias power source. This method is directed to improve the bottom coverage. The IMP deposition has attracted attentions as an approach that can achieve fast deposition with a shorter T-S distance as compared with the long throw sputtering.
For the CVD technique, Cu (tms) is dominant for now. However, to use Cu (tms) requires the substrate heated to a high temperature (at least 600.degree. C.). This is the temperature with a possibility of destroying components on the substrate. Such a high temperature may cause a problem if an organic material is used for a stopper (capacitor) in the future as a measure against delay in the manufacture of LSIs. Furthermore, the gases used for the process is detrimental to the human body. The cost for processing these gases and management therefor pose a problem.